70 Proceedings of Royal Society of Edinburgh. [sess. 
the wind, now hove to close to the water, and near enough to the 
ship for the most definite scrutiny, and then going ahead and up- 
wards if they pleased, not flapping a wing once for hours, I may 
swear ! — all in such a way as to be dumbfoundering, unless it be 
possible to suppose an ascending current apparently uniformly dis- 
tributed over a level ocean, and reaching to at least 50 or 60 feet 
above it, and with a rate of ascent sufficient to explain the birds’ 
behaviour. This supposition is prima facie an inadmissible one, 
for the air, if it was all ascending , would leave a vacuum over 
the water. 
“ At first I thought that the retarding action of the water friction 
(which was plainly enormous, for it was tearing the water surface 
to tatters) might explain the action by the circumstance that the 
retardation would crumple up the lower air strata endways, and 
by thickening them, would in effect produce an ascending motion 
in them. 
“ But in spite of the more vigorous frictional action close to the 
water surface, the ascent of the particles due to the crumpling up 
would be nil at the surface ; yet the birds seemed to find the ascent 
as active there as anywhere. Still I think there is something in 
this view. 
“ Two days later, however, when the gale was a good bit more 
furious, I had a better proof of what was happening, though the 
‘ how it happened ’ is still a puzzle. 
“ You know how in a heavy gale the sea surface seems to drift 
like dust ? Well, in this case, the air was for a long time so full 
of sea spray up to a level of 50 or 60 feet, that it looked as if a 
heavy April shower was passing, though there was a clear blue sky 
overhead, and sunshine. 
“ Now, whatever could carry spray to that height would answer the 
birds’ purpose. To-day the birds are again about, but the wind is 
only a double reef cutter breeze, if so much ; and to-day, though 
they do a good deal of skimming, they have also to do a great deal 
of flapping at intervals.” 
As an explanation of the ascent of the particles of spray, Mr 
Broude goes on to suggest that the frictional eddies in the air must 
receive their most effective renewal of energy from the friction on 
their under sides nearest the water surface, and that consequently their 
